Uh... yeah, that's kind of a silly question.
React was created by Facebook for use at Facebook, and shared with the community. The React team builds React openly, invites contributions from the community, and deliberately shares work on the project with the community, but they also have to work with Facebook's product teams to meet Facebook's internal needs.
There's a great writeup of React's history at https://facebook.github.io/react/blog/2016/09/28/our-first-5... .